Here is a good video that shows you how to use gparted. In the video he moves the swap partition to the end of the space on the SD Card. With the flash plugin and the rpi image we are not using a swap partition. But we do have a rrdcached partition. If you mount another device (usb hard drive or whatever) you no longer need this rrdcached partition. The reason it is used is because when no device is mounted there are errors produced. This is why Aaron added the rrdcached partition and mounted it. If you do not plan on mounting other device you can move the rrdcache partition to the end instead of the swap like he did in this video. Then you can resize the OS partition and apply the changes.